1. Field of the Invention
This invention relates to internal mould release compositions and to their use in the production of moulded articles by the reaction injection moulding process from reaction mixtures containing organic polyisocyanates and isocyanate-reactive components. In particular, it is directed to blends of organic metal salts and polysiloxane derivatives having pendant hydroxy functional organic groups and/or other isocyanate reactive groups.
2. Description of Related Art
The production of moulded articles, for example automotive body parts, from organic polyisocyanates and isocyanate-reactive components by the reaction injection moulding (RIM) process is well established. In the process, two highly reactive liquid streams, one containing a polyisocyanate and the other containing isocyanate-reactive components, for example polyol and/or polyamine reactants, are impingement mixed and rapidly injected into a mould cavity. By this method, high production rates of moulded polyurethane, polyurea and related polymeric articles having excellent physical properties can be achieved.
Whilst the RIM process is eminently suited to the mass production of isocyanate-based moulded articles, it is essential to its successful and economic operation that the moulded product can be easily removed from the mould without being damaged. One method of facilitating demoulding is to coat the internal surfaces of the mould with a mould release agent, for example a wax or soap. This procedure has the disadvantage that application of the release agent has to be repeated almost every time the mould is used, adding substantially to the time and cost of the process.
In order to overcome the problems associated with external mould release agents, it has been proposed to use release agents of the internal type pre-blended with either the polyisocyanate or the isocyanate-reactive component. One type of internal release agent which has been successfully used in the production of other moulded plastics articles comprises metal carboxylates such as zinc stearate.
Unfortunately, such salts are soluble in neither the polyisocyanate nor with most of the usual isocyanate-reactive components. It has been proposed, therefore, to use the metal salts in conjunction with certain materials which have the effect of compatibilising the salts with the isocyanate-reactive compounds: U.S. Pat. Nos. 4,876,019; 4,519,965; 4,581,386; 4,585,803. Furthermore, U.S. Pat. Nos. 4,477,366; 4,498,929; 4,504,313 and 4,546,154 propose the use of polysiloxane polymers having isocyanate reactive functional groups as internal mould release agents.